Abstract
Background
Transcatheter closure of patent ductus arteriosus (PDA) is a widely practiced procedure using various duct occluder devices.
Objective
To assess the safety and efficacy of the Cocoon Duct Occluder for PDA closure.
Methods
This single-arm cohort study, conducted in the Pediatric Cardiology Departments of NICVD Karachi, TMK, and Sukkur, included both prospective and retrospective recruitment. Using non-probability consecutive sampling, a minimum sample size of 35 was calculated to achieve a 90 % success rate with a 95 % confidence level. A total of 195 patients met the inclusion criteria over 2.5 years. Comprehensive preprocedural assessments were performed, including medical history, clinical examination, electrocardiography, chest X-ray, full blood count, and detailed echocardiographic measurements of PDA dimensions and left ventricular function. Procedures were performed by experienced pediatric cardiologists.
Results
PDA closure was successfully achieved in 186 of 195 patients (95.3 %). The most common PDA type was Type A (86.6 %), followed by Type B (4.6 %), Type C (2.6 %), Type D (3 %), and Type E (3 %) per Krichenko’s classification. Minor complications included peripheral vascular injury (6.6 %), arterial thrombosis (4 patients), venous thrombosis (7 patients), and arrhythmias (5 patients: 4 with supra-ventricular tachycardia [SVT] and 1 with ventricular tachycardia [VT], of which 2 SVT cases required adenosine therapy). One major complication, i.e. infective endocarditis, and no other major complications, such as device embolization or vascular injury, were observed.
Conclusion
The Cocoon Duct Occluder is a safe and effective device for PDA closure across all anatomical types. The procedure’s success is enhanced through meticulous device sizing, proper technique, and operator experience, minimizing the risk of major complications.
Highlights
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Effective PDA Closure: The Cocoon Duct Occluder demonstrated high success rates across various PDA types.
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Multi-Center Study: Data from multiple centers ensured diverse patient representation and reliable findings.
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Safe & Minimally Invasive: The procedure had minimal complications, confirming the device’s safety.
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Sustained Long-Term Outcomes: Follow-up data showed durable PDA closure and positive clinical results.
1
Introduction
Transcatheter closure of Patent Ductus Arteriosus (PDA) has emerged as a highly effective and widely accepted alternative to surgical ligation, particularly in patients with favorable anatomy [ ]. Advances in device technology have continuously enhanced the safety and efficacy of this minimally invasive approach. Among these innovations, the Cocoon Duct Occluder (CDO) offers a promising solution for PDA closure, warranting a focused evaluation of its potential advantages and clinical outcomes.
The CDO is a self-expanding device constructed from platinum-coated Nitinol, providing several design features aimed at optimizing its performance. The mushroom-shaped configuration, with a retention disk at the aortic end that is 4 mm larger than the quoted device size, ensures secure positioning and minimizes the risk of migration. Its main cylindrical body is filled with polyester fabric and reinforced with polypropylene patches, promoting effective thrombosis and ductal closure. The platinum nano-coating enhances biocompatibility by preventing nickel release, improving radiopacity, and facilitating precise fluoroscopic positioning [ ] ( Fig. 1 ).
The Cocoon device is delivered via a sheath system with sheath sizes ranging from 6F to 10F and includes a delivery cable, loader, and dilator for straightforward deployment and recapture. Clinical data underscore its efficacy, showing occlusion rates of 78.3 % on the first day, 90 % at one month, and 100 % at one year. Importantly, these outcomes are achieved without significant complications or detectable nickel release, making the CDO particularly suitable for patients with metal sensitivities [ ].
This study aims to evaluate the immediate, short-term, and long-term outcomes of PDA closure using the Cocoon Duct Occluder, with a particular emphasis on its application across various PDA morphologies. While transcatheter PDA closure is well-established, limited data exist regarding the Cocoon device’s performance in a real-world clinical setting, particularly in Pakistan. By systematically assessing the safety, efficacy, and complication rates associated with the Cocoon device, this research seeks to fill critical gaps in the existing literature and contribute to evidence-based recommendations for its use.
The Cocoon device design and material composition offer potential advantages over traditional devices such as the Amplatzer Duct Occluder. These include enhanced biocompatibility, improved radiopacity for precise positioning, and reduced risks of migration and metal-related sensitivities. By focusing on these attributes and analyzing clinical outcomes, this study will provide valuable insights into the Cocoon Duct Occluder’s role in advancing the transcatheter management of PDA.
2
Procedure
After obtaining informed consent, patients were transferred to the catheterization lab. Cardiac catheterizations were carried out with sedation, following our institutional protocol; for all babies, midazolam and ketamine were given to achieve conscious sedation based on their age and level of cooperation. Before the procedure, prophylactic antibiotics were given to all patients, and during the procedures, the patients were heparanized with 50–100 IU/kg after the arterial sheath placement. Sheaths were inserted into both the right femoral vein and artery on the right side after the application of local anesthetics. In a few cases where right side cannulation was not possible, left side femoral vein or artery cannulation was done. A pigtail 4,5 or 6 Fr catheter was used to perform an aortogram in the left lateral 90 projection, which provided a full lateral view to assess the position, anatomy, shape, length, and size of the PDA. In most cases, this projection was enough to decide on device closure. In some patients, a right anterior oblique injection was also given to increase the visualization of the ductus anatomy and size. Device size selection adhered to the manufacturer’s guidelines, with the device size chosen to be 2 mm larger than the narrowest PDA diameter. Following angiographic evaluation, hemodynamic data were collected, including aortic and pulmonary pressures. If pulmonary artery pressures were within the normal range, no further data were gathered. However, if abnormalities were noted, detailed data, such as the ratio of pulmonary to systemic blood flow (QP/QS) and pulmonary vascular resistance, were obtained. A multipurpose catheter was then advanced through the PDA from the pulmonary side into the descending aorta and subsequently exchanged with a delivery sheath using a 0.035″ exchange length 260 cm wire. The appropriate device was passed through the delivery sheath into the descending aorta, and the aortic end of the device was deployed first. All the PDAs were accessed using the antegrade approach. None of them required the retrograde approach.
The sheath and device were then pulled back as a single unit, allowing the rest of the device to be uncovered within the duct. A post-device deployment aortogram was performed to confirm the device position and evaluate for any residual leak or misplacement. In case of a large leak or misplacement, the device was retrieved into the delivery system and tried again in a proper position. The device was released once acceptable positioning was confirmed.
Adverse events were recorded, including procedural complications relating to vascular access and procedural catheter-related complications including hemodynamic instability or arrhythmia, device deployed in unsatisfactory position or embolization post-deployment, hemolysis, stroke, coarctation of aorta (narrowing and gradient of >20 mmHg between ascending and descending aorta), left pulmonary artery stenosis (narrowing and gradient of >20 mmHg between proximal and distal parts) and death. Post-procedure vital signs, wound site along distal pulses were monitored. Post-procedure echocardiography was done before discharge, and all patients were then followed for one year at intervals of 1 month, 6 months, and 1 year.
For patients followed retrospectively all data, angiograms, and echo were reviewed independently by two experienced cardiologists to ensure accuracy and reliability. Furthermore, interobserver agreement was assessed, demonstrating strong concordance between the reviewers.
3
Materials and methods
This was a single-arm cohort study, including both prospective and retrospective patient recruitment. The study was conducted in the Pediatric Cardiology Departments of NICVD Karachi, Tando Muhammad Khan (TMK), and Sukkur. A non-probability consecutive sampling technique was employed. Based on an expected 90 % PDA closure success rate using the Cocoon Duct Occluder, with a 95 % confidence level and a 10 % margin of error, the minimum required sample size was calculated to be N = 35 .
Patients who met the inclusion criteria and provided informed consent, following approval by the ethical review committee, were included. A pre-designed questionnaire was used to collect demographic data, anthropometric measurements, and clinical history. The preprocedural assessment involved medical history, physical examination, chest X-ray, full blood count, trans-thoracic echocardiography (2D and Color Doppler) to evaluate PDA morphology and size, and M-mode echocardiography to assess left ventricular function. All angiograms were interpreted by an expert cardiologist.
The study included two and a half years of prospective and retrospective data collection (January 2022 to July 2024).
Inclusion Criteria
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Patients aged 6 months to 18 years.
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Weight ≥ 6 kg.
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PDA with the narrowest diameter between 2 and 16 mm.
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Left-to-right shunting PDA.
Exclusion Criteria
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Patients outside the inclusion criteria.
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Associated congenital heart defects requiring surgery (e.g., ASD, VSDs, coarctation).
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Duct-dependent lesions.
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Pulmonary hypertension{PVRI > 8 WU} [ ].
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Active endocarditis.
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Right-to-left shunting through PDA.
3.1
Ethical considerations
This study has been reviewed and approved by the Institutional Review Board (IRB) of the National Institute of Cardiovascular Diseases (NICVD) under approval number Ref#: IRB-51/2024.
3.2
Data analysis
Data were analyzed using SPSS 2023. Quantitative data were summarized using mean, median, mode, and standard deviation. Frequencies and percentages were calculated for categorical variables.
4
Results
In our study, 195 patients underwent attempted patent ductus arteriosus (PDA) device closure over a two-and-a-half-year period, achieving a success rate of 95.3 %. 4.7 % percent of the PDAs did not undergo device closure as 3 patients had hairline PDAs and 6 patients had PVR of >8 woods. PDA was slightly more common in females, with 58 % of patients being female. The mean weight of the patients was 10.3 ± 1.5 kg, and the mean age was 2.5 ± 0.3 years. Associated defects and comorbidities were rare and did not significantly impact procedural outcomes. Most patients (85.6 %) had a minimum hospital stay of two days, including pre-procedure time. However, 19 (9.7 %) patients experienced prolonged hospitalization due to post-procedure arterial or venous thrombosis, requiring over three days of observation. Regarding anesthesia, the majority of patients underwent conscious sedation with ketamine and midazolam as needed, while only two patients required tracheal intubation and general anesthesia.
According to the angiographic classification by Krichenko et al., type A PDA was the most prevalent, observed in 169 patients (86.6 %). Type B PDA was present in 9 patients (4.6 %), type C in 5 patients (2.6 %), type D in 6 patients (3 %), and type E in 6 patients (3 %). The mean narrowest point of the PDA was 6 ± 2 mm, while the mean pulmonary artery (PA) end diameter was 8 ± 3 mm ( Table 1 ), ( Figs. 2, 3, 4, 5 ).
| Metric | Value | Notes |
|---|---|---|
| Total Patients | 195 | |
| Female Patients | 58 % | Slightly more common in females |
| Mean Age | 2.5 ± 0.3 years | |
| Mean Weight | 10.3 ± 1.5 kg | |
| PDA Types (Krichenko Classification) | Type A: 86.6 % (169 patients) | Type B: 4.6 % (9), Type C: 2.6 % (5), Type D: 3 % (6), Type E: 3 % (6) |
| Mean Narrowest PDA Diameter | 6 ± 2 mm | |
| Mean Pulmonary Artery End Diameter | 8 ± 3 mm |
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